Foster families provide respite and care for some of the most vulnerable children in society. This includes around three quarters of the 69,000 children who are looked after by social services in England. Get a foster placement right and the effects on a child can be nothing short of miraculous. But when it goes wrong, the results can easily reinforce prior placement breakdowns, disrupt friendships in a new school and exacerbate emotional, behavioural and relationship problems.

Families, professionals and commissioners are understandably keen to promote stable foster placements wherever possible. Yet the proportion of fostered children who moved placements three or more times in the past year – a key performance indicator for children’s social services – has been stuck at around 11% since 2010.

Social work teams are seeking more evidence-based solutions. Multidisciplinary work is especially important given the wide-ranging implications of placement breakdown for service providers. Producing evidence and offering consultation in this area are important parts of our work as academics and clinicians in child and adolescent mental health services (CAMHS).

Together with colleagues from King’s College London and South London and Maudsley NHS foundation trust, and with part funding from Lambeth’s child and adolescent looked after service, we carried out a systematic review of the international research on foster placement instability. The review put together evidence from 58 separate studies (22 from the UK) in order to define a comprehensive set of vulnerability and protective factors for foster placement instability and draw inferences about how different factors might undermine and promote stable placements. We have also worked with local social workers to translate the findings into new assessment and case planning tools.

Not surprisingly, the evidence shows a good long-term relationship with a social worker is vital for managing the transition to, and placement in, a new family. Unfortunately, the opposite also seems to be true in that inconsistent social work input (such as changing allocated workers) increases the likelihood of negative outcomes. Social workers can promote stability by involving children more actively in decision-making and placing a strong emphasis on education.

Preparation is especially important when integrating a new child. Foster carers – and other children in a foster family – need to be well informed about the child that will soon arrive. If at all possible, placement with extended family (kinship care) or siblings can maintain a continuing sense of family at a time of immense change. Avoiding residential care as a first placement (ideally exploring kinship first, foster care second) again increases the likelihood of a placement working out. But no consistent pattern emerged from studies looking at links between stability and frequency of contact with the child’s birth parents.

One of the encouraging findings of our review is that much can be done to promote stability through careful selection, training and support of foster carers. Personal attributes of carers like tolerance, persistence, flexibility and kindness are linked with more stable placements. Older and more experienced foster carers also tend to provide more stability.

Education emerged as another important influence on placement outcomes. School can be used as a springboard for young people’s personal development, helping them build confidence and make friends. Social workers and foster carers should do their utmost to raise academic expectations and encourage school participation, engagement and attainment.

In terms of the characteristics of the child, age was one of the most commonly identified factors in placement instability. Unfortunately older children are often harder to place in foster homes. They may have gone through multiple placement breakdowns already (especially if there has been hyperactivity or other behavioural problems). This requires sustained and patient efforts to re-build trust between the child and significant adults in their life.

Early recognition of mental health difficulties and timely evidence-based interventions can go a long way towards alleviating poor outcomes in late childhood and adolescence. Yet too often, emotional and behavioural symptoms are seen by frontline staff as “normal” reactions given a child’s history. In some cases, normalising short-term distress and dysfunction and taking a “wait and see” approach would be appropriate. But for more severe and persistent mental health issues, there is a danger in ruling out referral to specialist CAMHS in favour of unproven psychosocial approaches or generic case work.

​We wouldn’t expect any single factor (or combination of factors) to trigger a placement breakdown. Rather, the evidence shows that placement instability is affected by the complex relationships between child, foster carer, social worker and other system characteristics. Adequate preparation and realistic expectations are key to coping with inevitable challenges in placements. By planning ahead – and with attention to the issues listed here – the probability of a good outcome can be much improved.​Daniel Michelson is principal research clinical psychologist at King’s College London and a departmental lecturer at the University of Oxford. Partha Banerjea is lead clinician at South London and Maudsley NHS foundation trust and consultant adolescent psychiatrist at Southwark CAMHS.